check engine INFINITI QX4 2001 Factory Service Manual

4 CHECK HO2S2 (REAR) GROUND CIRCUIT FOR OPEN AND SHORT
1. Check harness continuity between HO2S2 terminal 4 and engine ground.
Refer to Wiring Diagram.
Continuity should exist.
2. Also check harness for short to power.
OK or NG
OK (With CONSULT-II)©GO TO 5.
OK (Without CONSULT-
II)©GO TO 6.
NG©Repair open circuit or short to power in harness or connectors
5 CHECK REAR HEATED OXYGEN SENSOR
With CONSULT-II
1. Start engine and drive vehicle at a speed of more than 70 km/h (43 MPH) for 2 consecutive minutes.
2. Stop vehicle with engine running.
3. Select ªFUEL INJECTIONº in ªACTIVE TESTº mode, and select ªHO2S2 (B1)/(B2)º as the monitor item with CONSULT-
II.
4. Check ªHO2S2 (B1)/(B2)º at idle speed when adjusting ªFUEL INJECTIONº to±25%.
SEF972Y
ªHO2S2 (B1)/(B2)º should be above 0.62V at least once when the ªFUEL INJECTIONº is +25%.
ªHO2S2 (B1)/(B2)º should be below 0.57V at least once when the ªFUEL INJECTIONº is þ25%.
CAUTION:
Discard any heated oxygen sensor which has been dropped from a height of more than 0.5 m (19.7 in) onto a
hard surface such as a concrete floor; use a new one.
OK or NG
OK©GO TO 9.
NG©GO TO 8.
DTC P0139, P0159 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(RESPONSE MONITORING)
Diagnostic Procedure (Cont'd)
EC-274

6 CHECK REAR HEATED OXYGEN SENSOR 2 (REAR)-I
Without CONSULT-II
1. Start engine and drive vehicle at a speed of more than 70 km/h (43 MPH) for 2 consecutive minutes.
2. Stop vehicle with engine running.
3. Set voltmeter probes between ECM terminal 72 (HO2S2 bank 1 right signal) or 71 (HO2S2 bank 2 left signal) and
engine ground.
4. Check the voltage when revving up to 4,000 rpm under no load at least 10 times.
(Depress and release accelerator pedal as soon as possible.)
SEF313XA
OK or NG
OK©GO TO 9.
NG©GO TO 7.
7 CHECK REAR HEATED OXYGEN SENSOR 2 (REAR)-II
Idle vehicle for 10 minutes, then check voltage between the same terminals as in Test No. 6; or check voltage when coast-
ing from 80 km/h (50 MPH) in ªDº position with ªODº OFF.
The voltage should go below 0.57V at least once during this procedure.
CAUTION:
Discard any heated oxygen sensor which has been dropped from a height of more than 0.5 m (19.7 in) onto a
hard surface such as a concrete floor; use a new one.
OK or NG
OK©GO TO 9.
NG©GO TO 8.
8 REPLACE REAR HEATED OXYGEN SENSOR
1. Stop vehicle and turn ignition switch ªOFFº.
2. Check heated oxygen sensor 2 (rear) harness protector color.
SEF372Z
CAUTION:
Before installing new oxygen sensor, clean exhaust system threads using Oxygen Sensor Thread Cleaner tool
J-43897-18 or J-43897-12 and approved anti-seize lubricant.
©Replace malfunctioning heated oxygen sensor 2 (rear).
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DTC P0139, P0159 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(RESPONSE MONITORING)
Diagnostic Procedure (Cont'd)
EC-275

Possible CauseNBEC0441IHarness or connectors
(The sensor circuit is open or shorted.)
IHeated oxygen sensor 2 (rear)
SEF189Y
DTC Confirmation ProcedureNBEC0158CAUTION:
Always drive vehicle at a safe speed.
NOTE:
If ªDTC Confirmation Procedureº has been previously conducted,
always turn ignition switch ªOFFº and wait at least 10 seconds
before conducting the next test.
WITH CONSULT-IINBEC0158S011) Turn ignition switch ªONº and select ªDATA MONITORº mode
with CONSULT-II.
2) Start engine and drive vehicle at a speed of more than 70 km/h
(43 MPH) for 2 consecutive minutes.
3) Stop vehicle with engine running.
4) Let engine idle for 1 minute.
5) Maintain the following conditions for at least 5 consecutive
seconds.
ENG SPEED 1,300 - 3,100 rpm
VHCL SPEED SE 64 - 130 km/h (40 - 80 MPH)
B/FUEL SCHDL 0.5 - 6.4 msec
COOLAN TEMP/S More than 70ÉC (158ÉF)
Selector lever Suitable position
6) If 1st trip DTC is detected, go to ªDiagnostic Procedureº,
EC-282.
SEF312XB
Overall Function CheckNBEC0159Use this procedure to check the overall function of the heated oxy-
gen sensor 2 (rear) circuit. During this check, a 1st trip DTC might
not be confirmed.
WITH GSTNBEC0159S011) Start engine and drive vehicle at a speed of more than 70 km/h
(43 MPH) for 2 consecutive minutes.
2) Stop vehicle with engine running.
3) Set voltmeter probes between ECM terminal 72 (HO2S2 bank
DTC P0140, P0160 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(HIGH VOLTAGE)
Possible Cause
EC-278

1 right signal) or 71 (HO2S2 bank 2 left signal) and engine
ground.
4) Check the voltage when racing up to 4,000 rpm under no load
at least 10 times.
(Depress and release accelerator pedal as soon as possible.)
The voltage should be below 1.4V during this procedure.
5) If NG, go to ªDiagnostic Procedureº, EC-282.
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DTC P0140, P0160 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(HIGH VOLTAGE)
Overall Function Check (Cont'd)
EC-279

Diagnostic ProcedureNBEC0161
1 INSPECTION START
1. Turn ignition switch ªOFFº.
2. Loosen and retighten engine ground screws.
SEF959Y
3. Check heated oxygen sensor 2 (rear) harness protector color.
SEF372Z
4. Disconnect corresponding heated oxygen sensor 2 (rear) harness connector.
SEF971Y
5. Disconnect ECM harness connector.
©GO TO 2.
DTC P0140, P0160 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(HIGH VOLTAGE)
Diagnostic Procedure
EC-282

2 CHECK HO2S2 (REAR) INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT
1. Check harness continuity between ECM terminal and HO2S2 terminal as follows.
Refer to Wiring Diagram.
MTBL0527
Continuity should exist.
2. Check harness continuity between ECM terminal or HO2S2 terminal and ground as follows.
Refer to Wiring Diagram.
MTBL0528
Continuity should not exist.
3. Also check harness for short to power.
OK or NG
OK©GO TO 3.
NG©Repair open circuit or short to ground or short to power in harness or connectors.
3 CHECK HO2S2 (REAR) GROUND CIRCUIT FOR OPEN AND SHORT
1. Check harness continuity between HO2S2 terminal 4 and engine ground.
Refer to Wiring Diagram.
Continuity should exist.
2. Also check harness for short to power.
OK or NG
OK©GO TO 4.
NG©Repair open circuit or short to power in harness or connectors.
4 CHECK HO2S2 (REAR) CONNECTORS FOR WATER
Check heated oxygen sensor connector 2 (rear) and harness connector for water.
Water should not exist.
OK or NG
OK (With CONSULT-II)©GO TO 5.
OK (Without CONSULT-
II)©GO TO 6.
NG©Repair or replace harness or connectors.
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DTC P0140, P0160 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(HIGH VOLTAGE)
Diagnostic Procedure (Cont'd)
EC-283

5 CHECK HEATED OXYGEN SENSOR 2 (REAR)
With CONSULT-II
1. Start engine and drive vehicle at a speed of more than 70 km/h (43 MPH) for 2 consecutive minutes.
2. Stop vehicle with engine running.
3. Select ªFUEL INJECTIONº in ªACTIVE TESTº mode, and select ªHO2S2 (B1)/(B2)º as the monitor item with CONSULT-
II.
4. Check ªHO2S2 (B1)/(B2)º at idle speed when adjusting ªFUEL INJECTIONº to±25%.
SEF972Y
ªHO2S2 (B1)/(B2)º should be above 0.62V at least once when the ªFUEL INJECTIONº is +25%.
ªHO2S2 (B1)/(B2)º should be below 0.57V at least once when the ªFUEL INJECTIONº is þ25%.
CAUTION:
Discard any heated oxygen sensor which has been dropped from a height of more than 0.5 m (19.7 in) onto a
hard surface such as a concrete floor; use a new one.
OK or NG
OK©GO TO 9.
NG©GO TO 8.
6 CHECK HEATED OXYGEN SENSOR 2 (REAR)-I
Without CONSULT-II
1. Start engine and drive vehicle at a speed of more than 70 km/h (43 MPH) for 2 consecutive minutes.
2. Stop vehicle with engine running.
3. Set voltmeter probes between ECM terminal 72 (HO2S2 bank 1 right signal) or 71 (HO2S2 bank 2 left signal) and
engine ground.
4. Check the voltage when revving up to 4,000 rpm under no load at least 10 times.
(Depress and release accelerator pedal as soon as possible.)
SEF313XA
OK or NG
OK©GO TO 9.
NG©GO TO 7.
DTC P0140, P0160 HEATED OXYGEN SENSOR 2 (REAR) (BANK 1)/(BANK 2)
(HIGH VOLTAGE)
Diagnostic Procedure (Cont'd)
EC-284

On Board Diagnosis LogicNBEC0169With the Air/Fuel Mixture Ratio Self-Learning Control, the actual
mixture ratio can be brought closely to the theoretical mixture ratio
based on the mixture ratio feedback signal from the heated oxygen
sensors 1 (front). The ECM calculates the necessary compensation
to correct the offset between the actual and the theoretical ratios.
In case the amount of the compensation value is extremely large
(The actual mixture ratio is too lean.), the ECM judges the condi-
tion as the fuel injection system malfunction and light up the MIL
(2 trip detection logic).
Sensor Input Signal to ECMECM func-
tionActuator
Heated oxygen sensors 1 (front)Density of oxygen in exhaust gas
(Mixture ratio feedback signal)Fuel injec-
tion controlInjectors
Malfunction is detected when fuel injection system does not oper-
ate properly, the amount of mixture ratio compensation is too large.
(The mixture ratio is too lean.)
Possible CauseNBEC0487IIntake air leaks
IHeated oxygen sensor 1 (front)
IInjectors
IExhaust gas leaks
IIncorrect fuel pressure
ILack of fuel
IMass air flow sensor
SEF968Y
DTC Confirmation ProcedureNBEC0170NOTE:
If ªDTC Confirmation Procedureº has been previously conducted,
always turn ignition switch ªOFFº and wait at least 10 seconds
before conducting the next test.
WITH CONSULT-IINBEC0170S011) Start engine and warm it up to normal operating temperature.
2) Turn ignition switch ªOFFº and wait at least 10 seconds.
3) Turn ignition switch ªONº and select ªSELF-LEARN CON-
TROLº in ªWORK SUPPORTº mode with CONSULT-II.
4) Clear the self-learning control coefficient by touching ªCLEARº.
5) Select ªDATA MONITORº mode with CONSULT-II.
6) Start engine again and let it idle for at least 10 minutes.
The 1st trip DTC P0171 or P0174 should be detected at this
stage, if a malfunction exists. If so, go to ªDiagnostic
Procedureº, EC-298.
7) If it is difficult to start engine at step 6, the fuel injection sys-
tem has a malfunction, too.
8) Crank engine while depressing accelerator pedal. If engine
starts, go to ªDiagnostic Procedureº, EC-298. If engine does
not start, check exhaust and intake air leak visually.
DTC P0171 (RIGHT, -B1), P0174 (LEFT, -B2) FUEL INJECTION SYSTEM
FUNCTION (LEAN)
On Board Diagnosis Logic
EC-294

SEF960Y
WITH GSTNBEC0170S021) Start engine and warm it up to normal operating temperature.
2) Turn ignition switch ªOFFº and wait at least 10 seconds.
3) Disconnect mass air flow sensor harness connector. Then
restart and run engine for at least 5 seconds at idle speed.
4) Stop engine and reconnect mass air flow sensor harness con-
nector.
5) Select ªMODE 7º with GST. Make sure 1st trip DTC P0100 is
detected.
6) Select ªMODE 4º with GST and erase the 1st trip DTC P0100.
7) Start engine again and let it idle for at least 10 minutes.
8) Select ªMODE 7º with GST. The 1st trip DTC P0171 or P0174
should be detected at this stage, if a malfunction exists. If so,
go to ªDiagnostic Procedureº, EC-298.
9) If it is difficult to start engine at step 7, the fuel injection sys-
tem has a malfunction.
10) Crank engine while depressing accelerator pedal. If engine
starts, go to ªDiagnostic Procedureº, EC-298. If engine does
not start, check exhaust and intake air leak visually.
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DTC P0171 (RIGHT, -B1), P0174 (LEFT, -B2) FUEL INJECTION SYSTEM
FUNCTION (LEAN)
DTC Confirmation Procedure (Cont'd)
EC-295

Diagnostic ProcedureNBEC0172
1 CHECK EXHAUST AIR LEAK
1. Start engine and run it at idle.
2. Listen for an exhaust air leak before three way catalyst.
SEF099P
OK or NG
OK©GO TO 2.
NG©Repair or replace.
2 CHECK FOR INTAKE AIR LEAK
Listen for an intake air leak after the mass air flow sensor.
OK or NG
OK©GO TO 3.
NG©Repair or replace.
3 CHECK HEATED OXYGEN SENSOR 1 (FRONT) CIRCUIT FOR OPEN AND SHORT
1. Turn ignition switch ªOFFº.
2. Disconnect corresponding heated oxygen sensor 1 (front) harness connector.
3. Disconnect ECM harness connector.
4. Check harness continuity between ECM terminal and HO2S1 terminal as follows.
Refer to Wiring Diagram.
MTBL0477
Continuity should exist.
5. Check harness continuity between ECM terminal or HO2S1 terminal and ground as follows.
Refer to Wiring Diagram.
MTBL0478
Continuity should not exist.
6. Also check harness for short to power.
OK or NG
OK©GO TO 4.
NG©Repair open circuit or short to ground or short to power in harness or connectors.
DTC P0171 (RIGHT, -B1), P0174 (LEFT, -B2) FUEL INJECTION SYSTEM
FUNCTION (LEAN)
Diagnostic Procedure
EC-298